The present invention relates to a turntable drive unit for use in microwave oven and more particularly, to a turntable drive unit for a microwave oven, which utilizes a shape memory alloy instead of a conventional drive motor. The shape memory alloy of the present invention deforms with the variation of temperature in a cavity and causes the rotative movements of the turntable.
Turntable drive units are known which utilize a motor which operates only with power supply for the driving turntable to rotate.
According to a prior art drive unit as shown in FIG. 2, an axle 5 of a turntable 2 is arranged to engage with the axle 11 of a high torque motor 4 and is mounted to an axial guiding member 7 having a slide bushing 8 between the axial guiding member 7 and the axle 5 for reduction of friction during rotation for driving to rotate itself. The axial guiding member 7 is to be kept by washers 9 and 10 from the separation.
However, since the eventual high load of such a drive unit requires an employment of a high torque motor which comprises a number of components to eventually bring up the cost price and the work hours for assembling, the prior art drive unit can be provided poor productivity and long delivery term of products.
Therefore, the device of the present invention eliminates such drawbacks of the prior art drive unit and is provided with a drive device without a motor. The drive unit of the present invention comprises a plate spring of a shape memory alloy which deforms to a certain limitation of the range in accordance to the variation of the temperature, and a coil spring of the same alloy, which is linked to an air adjusting plate. The air adjusting plate controls by means of air supply so that the temperature of the spring box makes to cause the expansion or contraction of the springs for the rotative operation of the turntable.